1. Field of the Invention
This invention lies in the field of manipulations of biological cells, and particularly methods for causing cells from a cell suspension to flow past a detection or treatment site in a single file or at a controlled rate.
2. Description of the Prior Art
Systems for detecting, analyzing, or transforming biological cells or other membrane-encased structures such as liposomes or vesicles are most often designed for batchwise operation. Transfection, for example, is typically performed in batchwise manner in a cuvette. Batchwise transfection involves manipulation of the cells and system components and repetitive processing steps, either by a laboratory technician or an instrument, and the quantity of cells or other structures that are transfected, as well as the rate at which the cells are processed, are subject to the size limitations of the typical cuvette. For these reasons, the processing of large volumes of sample and large numbers of structures is costly and prone to error. In procedures in which transfection is performed by electroporation, the repeated use of an electroporation chamber can cause overheating of the chamber, and the use of an overheated chamber can cause irreparable rupture of the cell membranes. Continuous-flow systems for electroporation have been contemplated but very little, if any, successful design work has occurred. The detection and characterization of cells by continuous flow, on the other hand, are commonly performed by flow cytometry. Although it is a well-known procedure, flow cytometry involves the use of costly fluidics components and the small channels through which the cells pass in flow cytometry instruments are susceptible to clogging.